Proximity sensors are used to detect the presence of an object without physical contact. For example, proximity sensors are implemented in switches to open and close an electrical circuit when they make contact with or come within a certain distance of an object. These sensors are most commonly used in manufacturing equipment, robotics and security systems. For example, in a production assembly line, a proximity sensor may be used to measure the position of a machine component. Whereas in robotics, the proximity sensor may be used to monitor a robot position in relation to an object or a place and use the information to steer the robot accordingly. In another common example, a proximity sensor is often used with a water faucet to automatically turn on and off the water when a person's hands are held within a predetermined distance of the water faucet.
In general, a proximity sensor may include an invisible light source and a photo detector. When an object comes within a predetermined distance of the proximity sensor, the object reflects the light from the light source to the photo detector. After sensing the light reflected by the object, the photo detector then sends an output signal indicating the presence of an object. Typically, an action is performed in response to the output signal, such as turning on the water faucet, turning on hand dryer, etc.
More recently, the proximity sensor has been widely adopted in automation equipment and on many small portable devices, such as cell phones, PDAs, etc. that accept integrated circuit packages with small footprints. Accordingly, the overall package size of proximity sensors must also become smaller. As the proximity sensors become smaller, it has become increasingly complex to manufacture these sensors in a mass production environment, which has resulted in high production costs. Therefore, a lighter weight and smaller profile proximity sensor that can be manufactured easily and inexpensively, while maintaining product performance and reliability is desirable.